Unexpected G4 Quicksilver Shutdown When Unattended

[SafetyAgentMan]

Dual 1 GHz Power PC G4 Mac OS X (10.3.7)

I was away for a few days and had unplugged my Quicksilver G4 while I was gone. When I returned I was not able to power up my G4. The power switch would light if you pressed it, but it would go out as soon as I removed my finger. I replaced the battery and reset the PMU which allowed me to power up the computer.

Everything appeared to be operating properly, but if I left the computer unattended for as little as 5 or 10 minutes I would come back to find the computer had shut down. The computer does not shut down if I am using it.

NOTE: My Energy Saver panel is set as follows:

• Put the computer to sleep when it is inactive for - NEVER

• Put the display to sleep when it is inactive for - NEVER

Next I suspected a power supply thermal problem and checked to see if all the fans were operating. I have 4 fans in my G4 and all except the one inside the power supply enclosure were operating.

I decided to pull the power supply and take it apart to check out the fan. On the bench with the fan connected to a 12Vdc supply it would not start unless I spun it with my finger and then its performance was anemic.

Next I ran down to the local electronics store and picked by an 80 x 80 x 25 mm fan with similar ratings to the defective fan in the G4 power supply. I replaced the fan, put everything back together and fired up the G4. Thinking my problem was solved I left the room to get some lunch. When I returned 10 minutes later the G4 was shut down again. Obviously replacing the battery, resetting the PMU and replacing the power supply fan has not resolved the shut down issue.

I tried running the Apple Hardware Test CD and I passed the quick test, but failed the extended test. I received the following results for the extended test.

Logic Board Error Detected

Error Code: Scc_/3/7

Since I am running a Sonnet Encore/ST G4 Duet dual processor card I am was not sure if the error code is due to the Apple Hardware Test not being able to check a non-Apple CPU or if there is an actual problem with the logic board.

Today I received the following e-mail from Sonnet:

You are correct in your assumption. The Apple Hardware Test CD is
designed to test "Apple" hardware. It fails miserably with 3rd party
hardware. So it pitches those weird error messages that mean nothing.
Put your old CPU in and run that test again and you'll not see those
errors.

If you need to test hardware, get a copy of the very excellent Tech
Tool Pro 4. It was designed to test both Apple and third party
hardware. That's why Apple includes it with their AppleCare program.

Sonnet Customer Service

I have run out of ideas. Can anyone shed some light as to why my computer is constantly shutting down without activity?

Thanks

[macworks]

Try unplugging any extra devices. How about pulling some RAM out? It's possible you have got a bad RAM chip -- and YES, I know it passed on the RAM test, but the hardware test often passes even though there is bad RAM. There may also be some corrosion in the CPU battery socket and when the battery is not connecting properly, you could experience erratic behavior. I would also try resetting the NVRAM with the following steps:
1) Shutdown computer (if it's on)
2) Power on the computer with the OPTION + COMMAND (apple) + O + F keys held down (that the letter O, not the number zero). Continue holding the keys until you boot into open firmware -- white screen, black text.
3) At the OF prompt, type 'reset-nvram' (no quotes) and press return. It should say "ok" almost instantly.
4) At the OF prompt type 'set-defaults' and press return.
5) At the OF prompt type 'reset-all'. The computer should reboot.

If none of these things works, try booting from a different startup disk and see what happens. If the computer works fine from a different startup disk, it's likely you have a problem on a software level with your normal boot drive or that hard drive is failing.

If all else fails, put the Apple processors back in, perhaps your Sonnet processor has failed.

[SafetyAgentMan]

Originally Posted by macworks

Try unplugging any extra devices. How about pulling some RAM out? It's possible you have got a bad RAM chip -- and YES, I know it passed on the RAM test, but the hardware test often passes even though there is bad RAM. There may also be some corrosion in the CPU battery socket and when the battery is not connecting properly, you could experience erratic behavior. I would also try resetting the NVRAM with the following steps:
1) Shutdown computer (if it's on)
2) Power on the computer with the OPTION + COMMAND (apple) + O + F keys held down (that the letter O, not the number zero). Continue holding the keys until you boot into open firmware -- white screen, black text.
3) At the OF prompt, type 'reset-nvram' (no quotes) and press return. It should say "ok" almost instantly.
4) At the OF prompt type 'set-defaults' and press return.
5) At the OF prompt type 'reset-all'. The computer should reboot.

If none of these things works, try booting from a different startup disk and see what happens. If the computer works fine from a different startup disk, it's likely you have a problem on a software level with your normal boot drive or that hard drive is failing.

If all else fails, put the Apple processors back in, perhaps your Sonnet processor has failed.

Christopher,

Thank you for all your suggestions. Looks like I am back up and running. I don't know what caused the last shut down after I installed the new power supply fan, but my system has been operating fine now for the last 18 hours. If anyone out there has an older G4 Quicksilver that is on all the time you may want to check out the power supply fan. My fan was in a locked rotor condition and was drawing 3 times the normal current from the 12Vdc supply. Besides not providing cooling the fan was also overloading the 12Vdc supply.

Picture of open power supply with new fan installed: http://www.fototime.com/22BFEF7DB2C5DFA/orig.jpg

Before I replaced the fan I had been noticing the sides of the CRT display shrinking slightly and quivering. After the fan replacement in the G4 the CRT display is rock solid. I suspect the overloaded 12Vdc supply in the G4 was causing problems for the video circuits also.

Howard